1. Field of the Invention
The present invention relates to a tamper proof slide bolt locking apparatus which provides protection for an associated padlock shackle.
2. Description of the Prior Art
A common apparatus for locking a movable structure such as a garage door against movement relative to a fixed structure such as a door frame employs a slide bolt attached to the door and slidable into a receptacle in the door frame. Preferably the apparatus is adapted for mounting at either side of the door for operation in either a left or right hand mode, that is, slidable to the left into a door frame located to the left of the door, or slidable to the right into a door frame located to the right of the door.
The typical slide bolt is bent or deformed to provide a central loop adapted to overlie an apertured staple attached to the door. The staple receives a padlock shackle to prevent the loop from being lifted off the staple, which is necessary for sliding the bolt back and forth. In this arrangement the padlock shackle is undesirably exposed to bolt cutters and the upper surface of the lock body can be struck with a hammer to forcibly dislodge the shackle.
One solution to the problem of such tampering is use of higher grade steel and heavier cross sections for the shackle, hasp and staple components, but this adds considerable expense to the locking system. Even such strengthened components are vulnerable to modern bolt cutters.
One type of locking device proposed in the prior art to deter such tampering employs a specially designed protective cover. The cover is either welded to or pivotally carried by the slide bolt. Separate hasp plates are welded to the cover and to the slide bolt mounting plate so they can be locked together by the padlock shackle. U.S. Pat. Nos. 4,031,719 (Klinger et al) and 3,953,062 (Maston) disclose devices of this type. Unfortunately, such specially formed and configured covers greatly increase fabrication costs, and make placement and removal of the padlock difficult. Typically the size of the space behind the cover for receiving the padlock is minimized to thwart insertion of bolt cutters. Consequently, user insertion of the padlock is awkward. The cover covers the shackle receiving openings and therefore makes location of the shackle in the openings difficult. Finally, although the cover provides protection against bolt cutters, it is susceptible to insertion of prybars and the like.